With the development of human society, communication devices and identification devices have become more and more widely used. The use of smart cards and associated identification devices has brought greatly improved safety and convenience to people's travel.
A smart card, also referred to as an IC card, is a portable plastic card with an IC chip adhered thereon or embedded therein. The card includes a microprocessor, an I/O interface and a memory, which provides functions of computing, access control and storage of data. The size and connecting terminals of the card are specified by relevant ISO standards such as ISO7810. Common smart cards include telephone IC cards, identification IC cards, and some transport tickets and memory cards.
The smart card includes a card body and a smart card module mounted on the card body. The smart card module includes a circuit board and electronic components (such as a chip) mounted on the circuit board. Due to its light weight, small thickness, the circuit board has been widely used in various electronic devices, such as cell phones, notebook computers, tablet PCs and liquid crystal displays (LCDs).
In currently available circuit board products, short-circuit accidents may occur when the gap between the adjacent pads is very small, so the gap need to be controlled. As the pads are square, the gap between the two adjacent pads is reflected by a distance between the two nearest border lines of the two adjacent square pads. However, in a high precision requirement, the distance between the border lines is not easy to be controlled. A minimum value of the distance between two adjacent pads 3 only can reach 75 um.
In addition, the pad (connecting pad) for soldering the chip is square in shape, while the gold ball for soldering of the chip is spherical. Therefore, the square pad causes a waste of pad material. Furthermore, the square pad occupies a large area of the polyethylene terephthalate (PET) film of the circuit board, which may result in less adhesive between the chip and the PET film and hence reduced reliability of the module.